1-N-LOWER ALKYLPIPERIDYL-1H-PYRAZOLO{8 3,4-b{9 PYRIDINES AND PYRIDINOLS

ABSTRACT

New 1-N-lower alkylpiperidyl-1H-pyrazolo(3,4-b)pyridines and pyridinols are useful as hypoglycemic agents.

Hoelm, Hans et al.

[111 3,755,331 Aug. 28, 1973 l-N-LOWER ALKYLPIPERIDYL-lH-PYRAZOLO[3,4- BlPYRIDINES AND PYRIDINOLS Inventors: Hoehn, Hans, Tegernheim; Ernst Schulze, Regensburg, both of Appl. No.: 55,250

US. Cl 260/293.6, 260/293.7, 260/293.87,

260/999 Int. Cl C07d 29/26 Field of Search 260/293.6

[56] References Cited UNITED STATES PATENTS 3,250,769 9/1966 Schmidt et al 260/24 7.]

Primary Examiner-Henry R. Jiles Assistant Examiner-G. Thomas Todd Attorney-Lawrence S. Levinson, Merle J. Smith and Donald J. Berrella 57] ABSTRACT New l-N-lower alkylpiperidyll H-pyrazoloI 3 ,4- b]pyridines and pyridinols are useful as hypoglycemic agents.

4 Claims, N0 Drawings l -N-LOWER ALKYLPIPERIDYL- l H-PYRAZOLO[ 3 ,4- B]PYRIDIN ES AND PYRIDINOLS SUMMARY OF THE INVENTION The symbols have the following meanings in formula I and throughout this specification: R is lower alkyl, R is hydrogen or lower alkyl, R;, is hydrogen or hydroxy, R is lower alkyl or phenyl and R is hydrogen or halogen.

Preferred are those compounds of formula I wherein R is lower alkyl, especially methyl, R is hydrogen or lower alkyl, especially methyl, R is hydrogen or hydroxy, R, is lower alkyl, especially methyl and R is hydrogen or halogen, especially bromine or chlorine. Also preferred are those compounds of formula I wherein R is methyl and R, is hydroxy.

DETAILED DESCRIPTION The new compounds of formula I are produced from S-aminopyrazoles of the formula by means of B-keto-acid derivatives of the formula wherein ALB is a group which may be converted to the structure in the 4-position of formula I and R is the same as previously defined.

When R is hydrogen in formula I, the

moiety in formula I" may be a dialkylacetal, e.g., an

acetaldehyde dialkyl acetal like acetylacetaldehyde dimethylacetal. When R is hydroxy in formula I, the

moiety in formula III may be a lower alkyl ester group, that is R represents a lower alkoxy group, e.g., C00- alkyl. The condensation reaction is effected at a temperature of about to 150C. in an inert solvent like glacial acetic acid, acetonitrile, formamides, polyphosphoric acid, etc.

The compounds of formula II are produced as described in British Pat. No. 1,057,740, published Feb. 8, 1967, by ring closure of an aldehyde or ketone hydrazone of the formula wherein R, and R are the same as previously defined. The cyclization is effected by heating at a temperature of about 90 to C. in an inert liquid organicsolvent, e.g., an alcohol like ethanol, butanol or the like, preferably in the presence of a catalyst, e.g., alcoholates like alkali metal alcoholates particularly butylates such as sodium butylate. Reaction of any of the products of formula I wherein R is hydrogen with at least two equivalent amounts of halogen, e.g., chlorine or bromine, in a solvent such as glacial acetic acid, chloroform, ethyl acetate or the like, yields a compound of formula I wherein R is the corresponding halogen.

The compounds of this invention are hypoglycemic agents which are effective in lowering blood sugar content in mammalian species such as mice, rats, rabbits, dogs or the like in a manner analogous to tolbutamide. Some are particularly noteworthy in their long duration of action. For this purpose a compound or mixture of compounds of formula I is administered orally or parenterally in a conventional dosage form such as tablet, capsule, injectable or the like. A single dose, or preferably 2 to 4 divided daily doses, provided on a basis of about 1 to 50 mg. per kilogram per day, preferably about 2 to 15 mg. per kilogram per day, is appropriate. These may be conventionally formulated in an oral or parenteral dosage form by compounding about 10 to 250 mg. per unit of dosage with conventional vehicle, excipient, binder, preservative, stabilizer, flavor or the like as called for by accepted pharmaceutical practice.

The following examples are illustrative of the invention. They illustrate the preparation of certain members of the group. Other compounds of the invention may be prepared by the same procedure with appropriate variation of the starting materials. All temperatures are on the centigrade scale.

EXAMPLE 1 3,6-Dimethyl- 1 l-methyl4-piperidyl)-1H- pyrazolo[3,4-b1pyridine 19.4 g. l-(l-methyl-4-piperidyl)-3-methyl-5-aminopyrazole (0.1mol.) and 13.2 g. freshly distilled acetyl acetaldehyde-dimethylacetal (0.1 mol.) in 38 ml. of glacial acetic acid are heated under reflux for hours. Subsequently, the acetic acid is removed by distillation in vacuo. The oily residue is then taken up in ether and the ethereal solution is neutralized by means of an aqueous ammonia solution, then dried with anhydrous sodium sulfate. After evaporation of the ether, the 3,6- dimethyll l-methyl-4-piperidyl)-1 H-pyrazolo-[B ,4- blpyridine is obtained at hp. 0.6 145146, yield 19.9 g. 81.5 percent of theory.

The hydrochloride is formed by adding to a solution of g. of the above obtained pyrazolopyridine in 13 ml. of anhydrous ether, with cooling, 15.5 ml. of an alcoholic solution of hydrogen chloride (6N). A white crystalline precipitate forms immediately. Yield 1 1.8 g. The product is allowed to air-dry overnight, mp. 263- 267 (dec.).

EXAMPLE 2 1-( l -Methyl-4-piperidyl )-6-phenyll H -pyrazolo[ 3 ,4- b pyridin-4-ol To 9 g. l-(1-methyl-4-piperidinyl)-5-aminopyrazole (0.05 mol.) in 40 ml. of glacial acetic acid there are added 9.6 g. of benzoylacetic acid ethyl ester (0.05 mol.). The mixture is refluxed for 5 hours, and subsequently the acetic acid is distilled off in vacuo. The oily residue is dissolved in dilute aqueous hydrochloric acid, activated charcoal is then added to the acid solution, the whole is stirred for 1 hour, subsequently filtered and the clear solution is neutralized by means of aqueous ammonia. A white crystalline precipitate forms immediately. Yield 10 g. 66 percent of the theory. After recrystallization from absolute alcohol, the l-( 1 -methyl-4-piperidyl)-6-phenyll H-pyrazolo[ 3.4- b]pyridine-4-ol melts at 245.5246.5.

EXAMPLE 3 3-Methyl-1-(1-methyl-4-piperidyl)-6-phenyl-lH- pyrazolo[3,4-b]pyridin-4-ol By substituting an equivalent amount of 1-( l-methyl- 4-piperidyl)-3-methyl-5-aminopyrazole for 1-( 1 methyl-4-piperidyl)-5 -aminopyrazole in the procedure of Example 2, 3-methyl-1-(l-methyl-4-piperidyl)-6- phenyl-1H-pyrazolo[3,4-b1pyridin-4-ol is obtained,

m.p., 25 l-253.

EXAMPLE 4 EXAMPLE 5 3,6-Dimethyl-l 1-methyl-4-piperidyl)-1H- pyrazolo[ 3 ,4-b ]pyridin-4-ol By substituting an equivalent amount of 1-( l-methyl- 4-piperidyl)-3-methyl-5-aminopyrazole for the 1-(1- methyl-4-piperidyl)-5-aminopyrazole in the procedure of Example 4, 3,6-dimethyl-1-(1-methyl-4-piperidyl)- lH-pyrazolo[3,4-b]-pyridin-4eol is obtained, m.p. 244-246.

EXAMPLE 6 5-Bromo-6-methyl- 1 1-methyl-4-piperidyl)-1H- pyrazolo[ 3,4'b]-pyridin-4-ol EXAMPLE 7 6-Methyl-1-( I-methyl-4-piperidyl)-1H-pyrazolo[3 ,4-

b]pyridine By substituting an equivalent amount of 1-( 1-ethyl-4- piperidyD-S-aminopyrazole for the 1-(1-methyl-4- piperidyl)-3-methyl-5-aminopyrazole, 6-methyll 1 ethyl-4-piperidyl)-1H-pyrazolo[3,4-b]pyridine is obtained.

What is claimed is:

l. A compound of the formula:

wherein R, is hydrogen or lower alkyl; R is lower alkyl or phenyl; R is hydrogen or halogen.

2. A compound as in claim 1 wherein R, is hydrogen, R is methyl and R is bromine.

3. A compound as in claim 1 wherein R, is methyl, R is phenyl and R is hydrogen.

4. A compound as in claim 1 wherein R, and R each is hydrogen and R, is phenyl. 

2. A compound as in claim 1 wherein R2 is hydrogen, R4 is methyl and R5 is bromine.
 3. A compound as in claim 1 wherein R2 is methyl, R4 is phenyl and R5 is hydrogen.
 4. A compound as in claim 1 wherein R2 and R5 each is hydrogen and R4 is phenyl. 